In extractive metallurgy autoclaves are used for increasing operating temperature. Once leached the discharge of the autoclaves is often reduced in temperature and pressure by allowing the autoclave discharge slurry to flash i.e. convert the heat of the slurry at high temperature into a flash steam.
The flash steam can be re-used to maximize energy efficiency. For example U.S. Pat. No. 5,489,326 discloses a pressure oxidation process for the recovery of gold wherein steam flashed from oxidized slurry is used to heat the autoclave feed. However, in operations where preheating of the autoclave feed is not required, for example in leaching sulphide concentrates, the flash steam is conventionally directly cleaned in a cleaning devises and released to atmosphere as low grade atmospheric steam. Energy and water is lost to atmosphere without recovery. Water loss from flash steam is also very significant as this water is not recovered.